Fidelity of protein synthesis does not decline during aging of cultured human fibroblasts.

To ascertain whether the fidelity of protein synthesis declines during cellular aging in vitro, we have developed a cell-free protein synthesizing system from cultured human fibroblasts which actively incorporates phenylalanine into acid-insoluble material upon addition of poly (U). The accuracy of poly (U)-directed protein synthesis was determined by comparing the ratio of leucine to phenylalanine incorporation in extracts of early- and late-passage fibroblasts derived from normal persons and from subjects with two genetic disorders of premature aging, progeria, and Werner syndrome. The results show no decline in translational fidelity at late passage or in prematurely aging cells, and thus fail to support the error catastrophe theory of cellular aging.